class Solution {
public:
    void reverseString(vector<char>& s) {
        int it1=0;
        int it2=s.size()-1;
        char tmp={};
        while(it1<it2){
            //   swap(s[it1],s[it2]);
            //   it1++;
            //   it2--;
            s[it1]^=s[it2];
            s[it2]^=s[it1];
            s[it1]^=s[it2];
            it1++;
            it2--;
        }
    }
};
